Atherosclerosis is a slowly progressing chronic inflammatory disease of the medium and large arteries that is responsible for high mortality rates in western society. Consequently, developing effective strategies to prevent or cure atherosclerosis is a highly significant objective that will profoundly impact human health care. At each stage of the disease, pro-atherogenic factors within the developing atherosclerotic lesion activate crucial cell types including endothelial cells (EC), smooth muscle cells and macrophages. When activated, these cells express cytokines, chemokines, cell surface molecules and enzymes that exacerbate atherogenesis. A major signaling mechanism associated with atherosclerosis is activation of the NF-kB family of transcription factors. Active NF-kB has been demonstrated in atherosclerotic plaques, and the importance of NF-kB for pro-atherogenic gene expression has been established in vitro. However, it remains unclear whether NF-:kB plays an overall positive or negative role during atherogenesis, and the effects of inhibiting NF-kB signaling on atherosclerosis in vivo are poorly understood. Furthermore, two major signaling mechanisms leading to the activation of distinct NF-kB species, named the classical and non-canonical NF-kB pathways, have been described recently. To date, only the classical pathway has been implicated in atherogenesis; however, emerging evidence strongly supports a role for the non-canonical pathway during the development of atherosclerosis. Our goal is to determine the overall effects of inhibiting NF-:kB signaling on the development of atherosclerosis. We will accomplish this using a combination of novel state-of-the-art pharmacological and genetic approaches that we have developed and by employing both in vitro and in vivo models of atherosclerosis. These approaches will provide both a deeper understanding of the molecular and biochemical mechanisms underlying disease progression and will determine the effectiveness of therapeutically blocking NF-kB in atherosclerosis. The hypothesis we will test is: Inhibiting NF-kB activation will prevent the development of atherosclerosis. We will address this by pursuing the following three specific aims: (1) To define the roles of EC-intrinsic classical and NC NF-kB signaling during atherogenesis; (2) To determine the role of classical and NC NF-kB activation in pro-atherogenic signaling and gene expression in EC; (3) To determine the effects of the NEMO binding domain (NBD) peptide on atherosclerosis in vivo. These studies will directly address the role of the non-canonical NF-kB pathway in atherogenesis for the first time. Furthermore, the NBD peptide has never been tested in vivo in models of atherosclerosis and we predict that this unique approach will demonstrate that systemically blocking classical NF-kB signaling prevents the development of atherosclerosis. Successfully accomplishing our aims will provide crucial novel insight into the potential therapeutic value of targeting classical and non-canonical NF-kB signaling in atherosclerosis patients. Consequently, our proposal is highly significant and broadly impacts a critical area of human health concern.